The Pierson's Puppeteers are sentient herd animals. They find that, as their numbers approach one trillion individuals, that their societ produces too much heat. What to do, what to do?

"I had explained," said Nessus, "that our civilisation was dying in its own waste heat. Total conversion of energy had rid us of all waste products of civilisation, save that one. We had no choice but to move our world outward from its primary."

"Was that not dangerous?"

"Very. There was much madness that year. For that reason it is famous in our history. But we had purchased a reactionless, inertialess drive from the Outsiders. You may have guessed their price. We are still paying in installments. We had moved two agricultural worlds; we had experimented with other, useless worlds of our system using the Outsider drive. In any case, we did it. We moved our world."

"In short, we found that a sun was a liability rather than an asset. We moved our world to a tenth of a light year's distance, keeping the primary only as an anchor. We needed the farming worlds and it would have been dangerous to let our world wander randomly through space. Otherwise we would not have needed a sun at all."

"We had brought suitable worlds from nearby systems, increasing our agricultural worlds to four, and setting them in a Kemplerer Rosette."

A Kemplerer Rosette (misspelled by Niven) was first described by W.B. Klemperer in 1962, in an article in The Astronomical Journal. See some very cool java applets that let you envision Kemplerer rosettes more easily.